1. Field of the Invention
The present invention relates to navigation methods. More particularly, this invention pertains to the navigation of aircraft equipped with high drift gyros for determining course which utilize an external course sensor that is subject to failure.
2. Background of the Prior Art
Course-and speed-supported inertial systems are employed in a number of aircraft. Often such systems employ relatively poor quality (large-drift gyros). An external course snsor such as a magnetic field detector (e.g. three-axis magnetometer) is employed for course support. In such systems, if the course support should fail, course and, thus, navigation error rapidly grow to unacceptably large amounts. A possible solution to this problem, the use of small drift gyros, is economically prohibitive in many cases.